A large field-induced strain of magnetic shape memory alloy is developed by the martensite variant reorientation. It is widely recognized that the martensite reorientation in a magnetic shape memory alloy (MSMA) can...A large field-induced strain of magnetic shape memory alloy is developed by the martensite variant reorientation. It is widely recognized that the martensite reorientation in a magnetic shape memory alloy (MSMA) can develop if the magnetic field is large enough. However, it has been shown in the literature that the magnetization rotation may block variant reorientation via energy minimization approach. In this paper, based on a micromechanicat model associated with the thermodynamic theory, authors show that there are some limits for the martensite reorientation, which is hindered by the magnetization rotation. Some useful conclusions are obtained.展开更多
In this paper, the mechanical responses of a thick-walled functionally graded hollow cylinder subject to a uniform magnetic field and inner-pressurized loads are studied. Rather than directly assume the material const...In this paper, the mechanical responses of a thick-walled functionally graded hollow cylinder subject to a uniform magnetic field and inner-pressurized loads are studied. Rather than directly assume the material constants as some specific function forms displayed in pre-studies, we firstly give the volume fractions of different constituents of the functionally graded material(FGM) cylinder and then determine the expressions of the material constants. With the use of the Voigt method, the corresponding analytical solutions of displacements in the radial direction, the strain and stress components, and the perturbation magnetic field vector are derived. In the numerical part, the effects of the volume fraction on the displacement, strain and stress components, and the magnetic perturbation field vector are investigated. Moreover, by some appropriate choices of the material constants, we find that the obtained results in this paper can reduce to some special cases given in the previous studies.展开更多
A simple hydration model is used here by taking the composition of the cement and the initial water: cementratio (w/c) into account explicitly. Its conceptual basis is a combination of the Avrami equation and Bentz’s...A simple hydration model is used here by taking the composition of the cement and the initial water: cementratio (w/c) into account explicitly. Its conceptual basis is a combination of the Avrami equation and Bentz’s modelbased on simple spatial considerations. In this model, the Avrami equation determines the initial reaction, andBentz’s model describes the following hydration stage. The model favors engineers for it relies on one experimentalparameter and has a reliable approximation in the practice.展开更多
Based on the micromechanical method and thermodynamic theory,a constitutive model for the macroscopic mechanical behavior of porous NiTi shape memory alloy is presented.The hydrostatic stress is considered for porous ...Based on the micromechanical method and thermodynamic theory,a constitutive model for the macroscopic mechanical behavior of porous NiTi shape memory alloy is presented.The hydrostatic stress is considered for porous NiTi according to the transformation function of dense NiTi.The present model takes account of the tensile-compressive asymmetry of NiTi,and can degenerate to model dense material.Numerical calculations,which only need material parameters of dense NiTi,are conducted to investigate the nonlinear and hysteretic strain of porous NiTi,and the predicted results are in good agreement with the corresponding experiments.展开更多
The drawing or rolling process endows polycrystal shape memory alloy with a crys- tallographic texture, which can result in macroscopic anisotropy. The main purpose of this work is to develop a constitutive model to p...The drawing or rolling process endows polycrystal shape memory alloy with a crys- tallographic texture, which can result in macroscopic anisotropy. The main purpose of this work is to develop a constitutive model to predict the thermomechanical behavior of shape memory alloy sheets, which accounts for the crystallographic texture. The total macroscopic strain is decom- posed into elastic strain and macro-transformation strain under isothermal condition. Considering the transformation strain in local grains and the orientation distribution function of crystallo- graphic texture, the macro-transformation strain and the effective elastic modulus of textured polycrystal shape memory alloy are developed by using tensor expressions. The kinetic equation is established to calculate the volume fraction of the martensite transformation under given stress. Furthermore, the Hill's quadratic model is developed for anisotropic transformation hardening of textured SMA sheets. All the calculation results are in good agreement with experimental data, which show that the present model can accurately describe the macro-anisotropic behaviors of textured shape memory alloy sheets.展开更多
A new constitutive model for describing the superelastic–plastic behavior of porous shape memory alloys(SMAs)is proposed.The model incorporates the influences of void shape and hydrostatic pressure as well as the ela...A new constitutive model for describing the superelastic–plastic behavior of porous shape memory alloys(SMAs)is proposed.The model incorporates the influences of void shape and hydrostatic pressure as well as the elastic modulus mismatch between austenite and martensite.In addition,the interactions between plastic strain and transformation strain are considered via the plastic back stress.The porous SMAs are considered as two-phase composites with the dense SMA matrix and the second phase representing ellipsoidal voids.Based on Gurson’s formulation,the transformation and plastic flow potentials accounting for the transformation–plasticity coupling are developed.The numerical results present good agreement with available experimental data for various levels of porosity,which proves that the model is capable of capturing stress-induced phase transformation and plastic deformation of porous SMAs.Using the proposed model,the influence of plastic strain on reverse transformation and the effects of porosity and void shape on the pseudoelastic and plastic behavior of porous SMAs are investigated.展开更多
基金supported by the National Natural Science Foundation of China (Nos.10772021 and 10972027)
文摘A large field-induced strain of magnetic shape memory alloy is developed by the martensite variant reorientation. It is widely recognized that the martensite reorientation in a magnetic shape memory alloy (MSMA) can develop if the magnetic field is large enough. However, it has been shown in the literature that the magnetization rotation may block variant reorientation via energy minimization approach. In this paper, based on a micromechanicat model associated with the thermodynamic theory, authors show that there are some limits for the martensite reorientation, which is hindered by the magnetization rotation. Some useful conclusions are obtained.
基金supported by the National Natural Science Foundation of China(No.11772041)
文摘In this paper, the mechanical responses of a thick-walled functionally graded hollow cylinder subject to a uniform magnetic field and inner-pressurized loads are studied. Rather than directly assume the material constants as some specific function forms displayed in pre-studies, we firstly give the volume fractions of different constituents of the functionally graded material(FGM) cylinder and then determine the expressions of the material constants. With the use of the Voigt method, the corresponding analytical solutions of displacements in the radial direction, the strain and stress components, and the perturbation magnetic field vector are derived. In the numerical part, the effects of the volume fraction on the displacement, strain and stress components, and the magnetic perturbation field vector are investigated. Moreover, by some appropriate choices of the material constants, we find that the obtained results in this paper can reduce to some special cases given in the previous studies.
基金The work was supported by Yunnan Local Colleges Applied Basic Research Projects(No.2018FH001-119)Science Research Foundation of Yunnan Education Department of China(Nos.2019J0734,2019J0733,2017ZZX177 and 2018JS422)+2 种基金the Candidate Talents Training Fund of Yunnan Province(Project No.2015HB064)National Natural Science Foundation of China(No.11802265)The authors(MBY and QLH)gratefully acknowledge the financial support from the Hundred Talents Program of Yuxi(Grant 2019).
文摘A simple hydration model is used here by taking the composition of the cement and the initial water: cementratio (w/c) into account explicitly. Its conceptual basis is a combination of the Avrami equation and Bentz’s modelbased on simple spatial considerations. In this model, the Avrami equation determines the initial reaction, andBentz’s model describes the following hydration stage. The model favors engineers for it relies on one experimentalparameter and has a reliable approximation in the practice.
基金supported by the National Natural Science Foundation of China (Nos. 10972027 and 10772021)Foundation of Jiangsu University(No. 11JDG066)
文摘Based on the micromechanical method and thermodynamic theory,a constitutive model for the macroscopic mechanical behavior of porous NiTi shape memory alloy is presented.The hydrostatic stress is considered for porous NiTi according to the transformation function of dense NiTi.The present model takes account of the tensile-compressive asymmetry of NiTi,and can degenerate to model dense material.Numerical calculations,which only need material parameters of dense NiTi,are conducted to investigate the nonlinear and hysteretic strain of porous NiTi,and the predicted results are in good agreement with the corresponding experiments.
基金Project supported by the National Natural Science Foundation of China(Nos.11272136,10902111,10772021 and 10972027)the Foundation of Jiangsu University(No.11JDG066)
文摘The drawing or rolling process endows polycrystal shape memory alloy with a crys- tallographic texture, which can result in macroscopic anisotropy. The main purpose of this work is to develop a constitutive model to predict the thermomechanical behavior of shape memory alloy sheets, which accounts for the crystallographic texture. The total macroscopic strain is decom- posed into elastic strain and macro-transformation strain under isothermal condition. Considering the transformation strain in local grains and the orientation distribution function of crystallo- graphic texture, the macro-transformation strain and the effective elastic modulus of textured polycrystal shape memory alloy are developed by using tensor expressions. The kinetic equation is established to calculate the volume fraction of the martensite transformation under given stress. Furthermore, the Hill's quadratic model is developed for anisotropic transformation hardening of textured SMA sheets. All the calculation results are in good agreement with experimental data, which show that the present model can accurately describe the macro-anisotropic behaviors of textured shape memory alloy sheets.
基金The authors acknowledge the financial support of National Natural Science Foundation of China(Grant no.11772041).
文摘A new constitutive model for describing the superelastic–plastic behavior of porous shape memory alloys(SMAs)is proposed.The model incorporates the influences of void shape and hydrostatic pressure as well as the elastic modulus mismatch between austenite and martensite.In addition,the interactions between plastic strain and transformation strain are considered via the plastic back stress.The porous SMAs are considered as two-phase composites with the dense SMA matrix and the second phase representing ellipsoidal voids.Based on Gurson’s formulation,the transformation and plastic flow potentials accounting for the transformation–plasticity coupling are developed.The numerical results present good agreement with available experimental data for various levels of porosity,which proves that the model is capable of capturing stress-induced phase transformation and plastic deformation of porous SMAs.Using the proposed model,the influence of plastic strain on reverse transformation and the effects of porosity and void shape on the pseudoelastic and plastic behavior of porous SMAs are investigated.